Glazing units frequently include two or more sheets of glass separated from one another by a space. The space (or insulating space) in between the sheets of glass can be filled with a gas (such as air, argon or krypton) to enhance insulating properties. A window spacer assembly is a structure that is frequently disposed between the sheets of glass around the periphery. The window spacer assembly serves various purposes. As one example, the window spacer assembly helps make the space between the sheets uniform around all of the edges. As another example, the window spacer assembly forms a gas-tight seal around the edges of the insulating space to hold the desired gas in place and prevent gas leakage. Failure of the seal provided by the window spacer assembly can lead to poor insulating performance and ingression of moisture into the insulating space. Moisture ingression into the unit can lead to moisture condensation on the glass surface, corrosion of coatings (such as low e coatings) or other defects.